How Can I Import MBOX File into Thunderbird?

Summary: Considering the useful features offered by Mozilla Thunderbird, users want to move to this free, open source email client. To migrate their emails and other data, they need to import the MBOX file into Thunderbird. This tutorial defines the detailed procedure on how to import MBOX file into Mozilla Thunderbird.

Thunderbird is a free desktop-based cross-platform email application that is developed by Mozilla Foundation. Similar to Microsoft Outlook, Mozilla Thunderbird allows the users to configure several email accounts by using IMAP or POP. The email application provides options to manage email, create contacts, tasks & calendar, and many others.

When you create a Thunderbird email account, the mailbox data is stored locally in the form of an MBOX file, which is one of the most extensively used file formats. Apart from Thunderbird, the MBOX file is used and supported by many email clients such as Spicebird, Netscape, Entourage, PocoMail, AppleMail, Sylpheed, Eudora, Evolution, Mulberry and SeaMonkey.

If you want to open an MBOX file without its parent email program, you need to import it into an MBOX compatible email application. Since Mozilla Thunderbird is a free, open source email application and compatible with both Windows OS and Mac OS, it is widely preferred to open the MBOX file. On the other hand, if you want to switch from one machine to another, you also need to move your Thunderbird profile to a new machine. In such a case, you also have to import the MBOX file data into the Thunderbird on the new machine.

How to Import MBOX file into Thunderbird?

If you are in the process of importing MBOX file into the Thunderbird, make sure that you have installed “ImportExportTools” add-ons to the Thunderbird.

If the ImportExportTools add-on is not installed, follow the given steps:

  • Download the importexporttools.xpi file from
  • Launch your Thunderbird application
  • Click on Menu >> Tools >> Extensions tab
  • Now click on the Gear icon and then select Install Add-on from file
  • Next, choose the importexporttools.xpi file that you’ve downloaded and install it
  • When installation is complete, restart your Thunderbird application

Now, let’s look at the MBOX to Thunderbird import process.

IMPORTANT: Before initiating the import process, it is recommended to back up the MBOX file as manual procedure is prone to data loss. So, taking the backup ensures that data can be restored in case of failure or if the file turns inaccessible. You can also convert the MBOX file to PST format by using an MBOX to PST Converter. It helps you to access the file in MS Outlook, in case it turns inaccessible or the Thunderbird client fails to import it.

Follow the steps below to import MBOX file into Thunderbird email client:

  • Launch Thunderbird by navigating to Programs and then Mozilla Thunderbird
  • Navigate to Tools and select ImportExportTools option from the given list
  • From the appeared list of options, select Import mbox file
  • When Files mbox import window appears, select Import directly one or more mbox files
  • Click OK to start the procedure to import MBOX to Thunderbird email client
  • If you want to import MBOX file with its subdirectories, then you can select the option that says Import one or more Mbox files, with its/ their subdirectory and click on the OK button
  • Next, browse the MBOX files from the location from where they are stored on the hard drive
  • Click on Open button to import the MBOX files to Thunderbird application

Now the MBOX file email messages are imported into Mozilla Thunderbird, you can access them anytime.

Limitations of Manually Importing MBOX File into Thunderbird

Though the given manual process can easily import the MBOX file into Thunderbird, it has some limitations also. If you’re trying to import your MBOX file into Thunderbird, you may face the following issues:

  • You may find that attachments are missing after the import process
  • There may be broken inline images
  • You may find some of the emails missing after the import
  • Incorrect header information

To overcome these limitations and data loss while importing MBOX file into Thunderbird, you can opt to convert the MBOX file to PST format by using a purpose-built software such as Stellar Converter for MBOX. The software converts MBOX to PST with utmost accuracy and all the items intact after conversion. You can then easily import the converted PST into any Outlook account and access the mailbox items.  


The MBOX file, apart from Mozilla Thunderbird, is created and supported by many other email clients such as Spicebird, Entourage, PocoMail, AppleMail, Eudora, SeaMonkey, etc. Sometimes, you want to migrate from one such email client to Thunderbird as it offers various useful features. For this, you need to manually import the mailbox data in MBOX file into Thunderbird, as mentioned in this post. However, the manual process often fails to import the attachments or any other emails items. In such a case, you can convert the MBOX file to PST by using a specialized MBOX converter tool. The tool helps to you retain all the mailbox items intact, along with attachments, while converting the MBOX to PST, which you can easily access by importing into Outlook.         

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